Permits (requests and grants) which have been field with the city since July 1998: http://pdd.eugene-or.gov/BuildingPermits/PermitSearch
Older permits must be requested from the city. There is generally a $20 fee for this, but having this history can be a great aid when looking at buying a property.

Property class and information for the sales of property for the last three years:

One way to indirectly evaluate contractors is to look at their closure rates on city permits. That is, how many permits have they successfully closed and is that typical for a contractor? How many have they left open?